Prince Harry is in mourning following the death of his friend and mentor, Jules Roberts, at 37.
The Duke was trained by Mr Roberts while preparing for his 2013 trek to the South Pole in aid of military charity, Walking With The Wounded.
Gruelling training, including spending 24 hours in an industrial freezer, was required to take part on the journey in a wider team which included Mr Roberts, an endurance expert.
He was found dead on August 5 and is believed to have died by suicide.
Both men were said to have instantly ‘hit it off’ upon meeting six years ago and forged a strong friendship before and during the 320-kilometre frosty journey.
“This has come as a real shock,” an insider told The Mirror.
“Jules helped to train Harry for the polar world... Harry even spent 24 hours in an industrial freezer to prepare.”
Although the prince didn’t attend the funeral, he sent a private note and flowers to Mr Roberts’ widow Francesca, and their two-year-old daughter.
The father-of-one worked as an executive at charity Sharegift, which allows people to turn shares into charitable donations.
Supporter of the royals
Mr Roberts also supported the royals financially — providing funding to their mental health campaign, Heads Together, upon its inception in 2016.
Walking With The Wounded founder Ed Parker paid tribute to the veteran trekker, saying he ‘was a diamond’.
"He was a properly good person with an energy beyond what you could imagine and everything was done with a huge great toothy grin," Mr Parker noted.
"I know that he admired hugely Harry's commitment to both mental health and the veteran community. There was a lot of respect both ways."